91 lines
2.5 KiB
TypeScript
91 lines
2.5 KiB
TypeScript
import {assertEquals} from "https://deno.land/std@0.224.0/assert/assert_equals.ts";
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import {AST, FunctionToken, printAST, readAST} from "./reader-printer.ts";
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type MalEnv = Map<string, FunctionToken>;
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function functionToken(fn: (...args: any[]) => any): FunctionToken {
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return { type: "function", value: fn };
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}
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function isBoolean(v: unknown): v is boolean {
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return v === true || v === false;
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}
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function isNumber(v: unknown): v is number {
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return typeof v === "number" && isFinite(v);
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}
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function isString(v: unknown): v is string {
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return typeof v === "string" || v instanceof String;
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}
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class REPL {
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private readonly env: MalEnv;
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constructor(env: MalEnv) {
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this.env = env;
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}
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static mathRepl(): REPL {
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const mathFunctions = new Map<string, FunctionToken>();
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mathFunctions.set("+", functionToken((a, b) => a + b));
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mathFunctions.set("-", functionToken((a, b) => a - b));
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mathFunctions.set("*", functionToken((a, b) => a * b));
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mathFunctions.set("/", functionToken((a, b) => a / b));
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return new REPL(mathFunctions);
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}
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read(source: string): AST {
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return readAST(source);
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}
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cast(value: unknown): AST {
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if (value === true || value === false) {
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return { type: "boolean", value: value };
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}
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if (isBoolean(value)) {
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return { type: "boolean", value: value };
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}
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if (isString(value)) {
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return { type: "string", value: value };
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}
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if (isNumber(value)) {
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return { type: "number", value: value };
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}
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throw new Error(`Unknown return type from functon: ${value}`);
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}
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eval_(ast: AST): AST {
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if (ast.type === "list") {
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const fn = this.eval_(ast.value[0]) as FunctionToken;
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const ret = fn.value(
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...ast.value.slice(1).map((n) => this.eval_(n).value),
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);
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return this.cast(ret);
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}
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if (ast.type === "sym") {
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const ret = this.env.get(ast.value);
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if (ret === undefined) {
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throw new Error(`Unknown reference ${ast.value}`);
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}
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return ret;
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}
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return ast;
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}
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print(form: AST): string {
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return printAST(form);
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}
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rep(source: string): string {
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return this.print(this.eval_(this.read(source)));
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}
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}
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Deno.test("basic", function (): void {
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const repl = REPL.mathRepl();
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assertEquals(repl.rep("(+ 1 1)"), "2");
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assertEquals(repl.rep("(+ 2 (* 3 4))"), "14");
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});
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